/*
 * Copyright 2002-2009 the original author or authors. Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language governing permissions and limitations under the
 * License.
 */

package org.springframework.http.converter;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.util.FileCopyUtils;

/**
 * Implementation of {@link HttpMessageConverter} that can read and write strings.
 * <p>
 * By default, this converter supports all media types (<code>&#42;&#47;&#42;</code>), and writes with a
 * {@code Content-Type} of {@code text/plain}. This can be overridden by setting the
 * {@link #setSupportedMediaTypes(java.util.List) supportedMediaTypes} property.
 * 
 * @author Arjen Poutsma
 * @since 3.0
 */
public class UTF8StringHttpMessageConverter extends AbstractHttpMessageConverter<String> {

    public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

    private final List<Charset> availableCharsets;

    public UTF8StringHttpMessageConverter() {
        super(new MediaType("text", "plain", DEFAULT_CHARSET), MediaType.ALL);
        this.availableCharsets = new ArrayList<Charset>(Charset.availableCharsets().values());
    }

    @Override
    public boolean supports(Class<?> clazz) {
        return String.class.equals(clazz);
    }

    @Override
    public String readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException {
        MediaType contentType = inputMessage.getHeaders().getContentType();
        Charset charset = contentType.getCharSet() != null ? contentType.getCharSet() : DEFAULT_CHARSET;
        return FileCopyUtils.copyToString(new InputStreamReader(inputMessage.getBody(), charset));
    }

    @Override
    protected Long getContentLength(String s, MediaType contentType) {
        if (contentType != null && contentType.getCharSet() != null) {
            Charset charset = contentType.getCharSet();
            try {
                return (long) s.getBytes(charset.name()).length;
            } catch (UnsupportedEncodingException ex) {
                // should not occur
                throw new InternalError(ex.getMessage());
            }
        } else {
            return null;
        }
    }

    @Override
    protected void writeInternal(String s, HttpOutputMessage outputMessage) throws IOException {
        outputMessage.getHeaders().setAcceptCharset(getAcceptedCharsets());
        MediaType contentType = outputMessage.getHeaders().getContentType();
        Charset charset = contentType.getCharSet() != null ? contentType.getCharSet() : DEFAULT_CHARSET;
        FileCopyUtils.copy(s, new OutputStreamWriter(outputMessage.getBody(), charset));
    }

    /**
     * Return the list of supported {@link Charset}.
     * <p>
     * By default, returns {@link Charset#availableCharsets()}. Can be overridden in subclasses.
     * 
     * @return the list of accepted charsets
     */
    protected List<Charset> getAcceptedCharsets() {
        return this.availableCharsets;
    }


}
